Radio frequency identification (RFID) is an area of automatic identification that has been gaining favor among a variety of industry groups in recent years and is now generally recognized as a means of enhancing data handling processes, complimentary in many ways to other data capture technologies such as bar coding. A range of devices and associated systems are available to satisfy a broad range of applications. Despite this diversity, the principles upon which RFID is based are quite straight forward, even though the technology and technicalities concerning the way in which it operates can be quite sophisticated.
The object of any RFID system is to store data in one or more of a variety of transponders, commonly known as tags, and to retrieve this data, by machine-readable means, at a suitable time and place to satisfy particular application needs. Data within a tag may provide identification for an item in manufacture, goods in transit, a location, and/or the identity of an animal or individual. By including additional data the prospect is provided for supporting applications through item-specific information or instructions immediately available upon reading the tag. For example, the color of paint for a car body entering a paint spray area on a production line can be encoded in a tag for reading (and subsequent utilization) as the car body enters the painting area.
In addition to the tags themselves, an RFID system requires some means of reading or interrogating the tags (often called a “reader” although it generally includes some form of transmitter for interrogating the tags) and some means of communicating the data to a host computer or information management system. A system may also include a facility for entering or programming data into the tags, if the manufacturer does not undertake this operation at the source. Quite often an antenna is distinguished as if it were a separate part of an RFID system. While its importance justifies this attention, antennas are perhaps better viewed as features that are present in both readers and tags, essential for the communication between the two.
Communication of data between tags and a reader is by wireless communication. Two common methods distinguish and categorize RFID systems, one based upon close proximity electromagnetic or inductive coupling and one based upon propagating electromagnetic waves. Recently, capacitive coupling schemes have also been introduced. In any event, coupling is via the antenna structures described above and while the term antenna is generally considered more appropriate for propagating systems it is also loosely applied to inductive systems.
FIG. 1A illustrates a conventional RFID system that relies on inductive coupling to transmit stored information to a reader. As shown, the tag 10 is placed so that its antenna 12 is within a radio frequency (RF) field created by the reader's antenna 14. As a current is passed through the antenna 14, the RF field 16 is generated. The area of the RF field 16 will depend on the amount of current passed through antenna 14, the type of materials that are used to construct antenna 14, and the size and type of antenna 14 that is used. As the tag's antenna 12 passes through the RF field 16, a current is generated in the antenna 12 and that current is used to power the tag components, resulting in the stored data being transmitted. If the reader uses a time varying current within antenna 14, this process will occur even if the tag 10 is stationary. Because the tag 10 does not include its own power source to carry out transmissions of data, the tag is referred to as a passive RFID tag.
FIG. 1B illustrates the use of an active tag 18, which allows for coupling through propagating electromagnetic waves. In this case, the tag 18 includes its own power source (e.g., a battery) which allows the tag to transmit its stored data to a reader antenna 20 directly, without having to rely on power generated from a radiated RF field. This allows for reading operations over extended ranges from that usually provided by passive tags that rely on inductive coupling.
To transfer data efficiently via the air that separates the two communicating antennas generally requires that the data be superimposed upon a carrier wave, as is common in the communication arts. This process is referred to as modulation, and various schemes are available for this purpose, each having particular attributes that favor their use. Commonly employed modulation techniques for RFID tags include amplitude shift keying (ASK), frequency shift keying (FSK) and phase shift keying (PSK). Common carrier frequencies include high frequencies (HF, approximately 3–30 MHz), very high frequencies (VHF, approximately 30–300 Mhz) and ultra high frequencies (UHF, frequencies above 300 MHz). Higher carrier frequencies allow for faster data rates, but are generally limited to line-of-sight applications. Commonly used commercial RFID systems operate at 13.56 MHz, while others operate at 915 MHz.
Having looked at some of the basics behind RFID technology, we turn now to some further details regarding the components that make up a conventional system. FIG. 2 illustrates an example of a conventional RFID system 22 that includes a transponder or tag 24 (which may be of the active or passive variety) with an antenna 26, and a reader/programmer 28 with an antenna 30. The word transponder, derived from the combination of TRANSmitter and resPONDER, reveals the function of the device. The tag 24 responds to a transmitted or communicated request for the data it stores by communicating information by wireless means across the space or air interface between the tag and the reader. The term also suggests the essential components that form an RFID system—tags and a reader or interrogator. Where interrogator is often used as an alternative to the term reader, a difference is sometime drawn on the basis of a reader together with a decoder and interface forming the interrogator.
The basic components of tag 24 are shown in FIG. 3. Generally speaking tags are fabricated as low power integrated circuits suitable for interfacing to external coils (i.e., antennas 26), or utilizing “coil-on-chip” technology, for data transfer and power generation (passive mode). Some analog circuitry 32 is generally included for these purposes. In addition, the tag may include a read-only memory (ROM) 34, random access memory (RAM) 36 and/or non-volatile programmable memory (often a form of Flash memory) 38 for data storage depending upon the type and sophistication of the device.
The ROM-based memory 34 is used to accommodate security data and the transponder operating system instructions which, in conjunction with the processor or processing logic 40, deals with the internal “house-keeping” functions such as response delay timing, data flow control and power supply switching. The RAM-based memory 36 may be used to facilitate temporary data storage during transponder interrogation and response. The non-volatile programmable memory 38 may take various forms, electrically erasable programmable read only memory (EEPROM) being typical. It is used to store the transponder data and needs to be non-volatile to ensure that the data is retained when the device is in its quiescent or power-saving “sleep” state.
Various data buffers (which are created in the volatile memory 36) may be used to temporarily hold incoming data following demodulation and outgoing data for modulation and interface with the tag antenna 26 (which itself is used to sense the interrogating field and, where appropriate, the programming field, and also serves as the means of transmitting the tag response to the interrogator). The interface circuitry 32 provides the facility to direct and accommodate the interrogation field energy for powering purposes in passive transponders and triggering of the tag response. Where programming is accommodated, facilities must be provided to accept the incoming data modulated signal and perform the necessary demodulation and data transfer processes.
RFID tags such as tag 24 come in a wide variety of physical forms, shapes and sizes. Animal tracking tags, inserted beneath the skin, can be as small as a pencil lead in diameter and ten millimeters or so in length. Tags can be screw-shaped to identify trees or wooden items, or credit card shaped for use in access applications (e.g., identity badges). The anti-theft hard plastic tags attached to merchandise in stores are a form of RFID tag, as are the heavy-duty rectangular transponders used to track inter-modal containers, or heavy machinery, trucks, and railroad cars for maintenance and tracking applications.
Returning to FIG. 2, the reader/interrogator 28 can differ quite considerably in complexity, depending upon the type of tags being supported and the functions to be fulfilled. However, the overall function is to provide the means of communicating with the tags 24 and facilitating data transfer (a process generally known as “scanning”). Functions performed by the reader 28 may include quite sophisticated signal conditioning, parity error checking and correction. Once the signal from a tag 24 has been correctly received and decoded, algorithms may be applied to decide whether the signal is a repeat transmission, and may then instruct the transponder to cease transmitting. This is known as the “Command Response Protocol” and is used to circumvent the problem of reading multiple tags in a short amount of time. Using interrogators in this way is sometimes referred to as “Hands Down Polling”. An alternative, more secure, but slower tag polling technique is called “Hands Up Polling”, which involves the interrogator looking for tags with specific identities, and interrogating them in turn. This and other contention management techniques have been developed to improve the process of batch reading. A further approach may use multiple readers, multiplexed into one interrogator, but with attendant increases in costs.
Transponder programmers are the means by which data is delivered to tags capable of being programmed/reprogrammed. Programming is generally carried out off-line, at the beginning of a batch production run, for example. However, in some systems reprogramming may be carried out on-line, particularly if a tag is being used as an interactive portable data file within a production environment, for example. By combining the functions of a reader/interrogator and a programmer into a single unit 28, data may be read and appended or altered in the tag 24 as required.
Potential applications for RFID are many and varied. The attributes of RFID are complimentary to other data capture technologies and thus able to satisfy particular application requirements that cannot be adequately accommodate by alternative technologies. Principal areas of application for RFID that can be currently identified include: transportation and logistics, manufacturing and processing, and security. A range of miscellaneous applications may also be distinguished, some of which are steadily growing in terms of application numbers. They include: animal tagging, waste management, time and attendance, postal tracking, and road toll management. As standards emerge, technology develops still further, and cost reduction has spawned considerable growth in terms of application numbers.
One field that has received some attention in the RFID arena is that of airline baggage handling. As any frequent traveler will recognize, the problem of ensuring that airline baggage is placed on the correct aircraft to meet its intended recipient at the end of a journey is still one that has yet to be satisfactorily addressed by the airline operators. Moreover, new security regulations imposed by the U.S. and other governments require that airlines ensure that a passengers baggage only be placed aboard an aircraft if the passenger him/herself boards. Although some schemes to address these problems have identified the desirability of using RFID tags, to date no scheme has been developed that can ensure, with a high degree of accuracy, that a piece of baggage or other cargo has actually been placed aboard the correct or intended aircraft.
For example, U.S. Pat. No. 6,222,452 to Ahlstrom and Johansson proposes a scheme wherein the movements of passengers and luggage are tracked through the use of RFID tags. In this scheme, when a passenger presents him/herself for check-in, an RFID tag is attached to the passenger's luggage to be checked. The RFID tag is encoded with the passenger's information (such as itinerary information). A similar RFID tag may be included in the passenger's boarding pass.
The passenger and his/her luggage then proceed toward the aircraft in the conventional fashion, with the luggage tag and boarding pass tag being “scanned” at various locations within the terminal (e.g., along luggage conveyor belts and at security checkpoints). Each time the passenger's boarding pass or luggage identification tag is scanned, an identification signal is transmitted to a central computer system for further processing. In this way, luggage and passengers can be correlated to one another.
Although the scheme proposed by Ahlstrom and Johansson may allow for detecting when a passenger whose luggage is placed on an aircraft does not him/herself board the aircraft, it does not provide any enhancement over the conventional methods of ensuring that luggage is actually placed on the aircraft for which it is intended. Stated differently, there is no mechanism (other than manual baggage handling procedures) for determining whether a piece of luggage has been placed aboard the correct aircraft.
U.S. Pat. No. 6,097,301 to Tuttle describes a scheme for using RFID tags with aircraft luggage wherein a human operator uses a wearable interrogator to obtain information regarding the pieces of luggage s/he is sorting. In this scheme, the two-way communication range between the interrogator transceiver and the tag transceiver is adjusted to only slightly exceed the closest distance between the interrogator and the tag while the operator is handling the tagged object. Preferably, the range is short enough that other tagged objects will remain outside the communication range and so will not respond to messages from the interrogator. In this way, false reads are purportedly reduced. By using similar interrogators at destination and arrival cities, the location of various baggage items can be determined. However, this scheme cannot ensure the reliable placing of a particular item of baggage on a specific aircraft because it relies on conventional manual baggage handling procedures.
U.S. Pat. No. 6,002,344 to Bandy et al. proposes a scheme for inventorying a number of RFID tags with permanent identification numbers to guard against time slot contention, but offers no suggestions for the problem at hand: Namely, ensuring that luggage finds its way onboard the proper aircraft or other transportation vehicle.
U.S. Pat. No. 5,933,098 to Haxton describes a security scheme wherein a system of scanners and transponders installed in an airport provide the ability to match a passenger with his or her baggage. At the baggage check-in counter, airline personnel issue conventional bar coded tags, which are subsequently attached to a passenger's baggage. This data is uploaded to a central computer. The passenger is also issued a boarding pass with a similar bar code. A bar code scanner located onboard the aircraft is then used to scan each boarding pass and the information therefrom is transmitted to the central computer to indicate that the passenger has boarded the aircraft. Baggage placed in containers for shipping on the flight is scanned in a similar fashion. Then, after all passengers are onboard and the aircraft doors closed, a boarding complete signal would be transmitted to the central computer. This signals a program in the computer to run a simple compare routine for each passenger and his or her baggage. If the compare program indicates that a passenger failed to board the aircraft, an alarm is automatically generated.
This system is similar to ones currently in use and as experience has demonstrated it does not provide a reliable means for ensuring that luggage is placed on the proper aircraft. Further, because of the manually intensive scanning processes involved, it is rather time consuming. In short, it does not address the needs of today's airlines and passengers.
U.S. Pat. No. 5,911,688 to Schaefe proposes that an RFID tag be fastened to each piece of baggage so that when the baggage item is checked by a traveler at an airport, identification information corresponding to a code printed on the traveler's boarding pass is stored in the tag. The traveler then proceeds to the gate of his flight, where the code printed on his boarding pass is read. The RFID tag transmits stored identification information, so that the baggage item is loaded onto the aircraft only when the code printed on the boarding pass has been read at the gate. In so far as this scheme proposes the use of active tags, it likely would not pass scrutiny under regulations governing the use of electronic devices in aircraft. Further, it does not ensure that the correct baggage is loaded aboard the correct aircraft.
U.S. Pat. No. 5,842,555 to Gannon and Graves proposes an automated baggage tracking and sorting system having a conveyor system controlled by a system controller, and a distributed baggage identification system. The distributed baggage identification system includes a number of zone content identifiers (RFID tags) coupled to one or more conveyors at predetermined locations to create a number of zones. Each of the zones is associated with one of zone content identifiers, and each of the zone content identifiers is configured to store information pertaining to the object located in the associated zone.
A number of information retrievers positioned adjacent to the conveyors at predetermined transition regions are configured to retrieve information from the zone content identifiers as the associated zone is at a transition region. A system controller utilizes the zone content information for identifying and tracking baggage traveling through the conveyor system. The system controller also transmits control commands to the conveyor system in accordance with routing decisions based upon the contents of the conveyor system zones.
Notably, although this system can be used to track baggage within a terminal, it does not provide for ensuring the delivery of that baggage to a designated aircraft. Nor does it provide for correlating baggage information with passenger information.
Other schemes including photograph and/or fingerprint identification schemes have addressed the need to match a passenger with his or her baggage and/or ticket, but for the most part these proposals have not addressed the problem of ensuring that baggage is placed aboard the correct aircraft.